The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Referring now to FIG. 1, a functional block diagram of an engine system 100 is shown. Air is drawn through a throttle valve 102 into an intake manifold 104. An air fuel mixture is created by injecting fuel from a fuel injector 106 into the intake manifold 104. The air fuel mixture is drawn through an intake valve 108 into a representative cylinder 110. An ignition coil 112 activates a spark plug 114 to ignite the air/fuel mixture within the cylinder 110. After ignition, an exhaust valve 116 allows the cylinder 110 to vent the products of combustion to an exhaust system 118.
A control module 120 receives signals from first and second throttle position sensors (TPS's) 122 and 124. The control module 120 outputs a control signal to an electronic throttle control (ETC) motor 126, which actuates the throttle valve 102. The control module 120 controls the fuel injector 106 and the ignition coil 112. The control module 120 monitors inputs, such as a position of a gas pedal (not shown), determines a desired throttle position, and instructs the ETC motor 126 to actuate the throttle valve 102 to the desired throttle position.
In general, the engine control module activates the ETC motor to position the throttle according to a desired throttle area determined in response to accelerator pedal position and various other control functions, such as idle speed control, engine governor control, cruise control, and traction control. Some engine control systems set indicated throttle to a higher one of the first and second TPS's during an out of correlation (OOC) error and/or fault. The OOC error occurs when a difference between the two TPS sensors is greater than a predetermined threshold.
An out of range (OOR) error may also occur. The TPS sensors may be set to provide a voltage output between first and second voltages. For example, a first TPS may provide a voltage between 0.5 V and 4.5 V corresponding to closed throttle and wide open throttle (WOT). The second TPS may provide a voltage between 4.5 V and 0.5 V corresponding to closed throttle and wide open throttle (WOT). Outputs of the first and second TPS may be input to a lookup table (LUT), which converts the voltages from both the first and second TPS to a percentage of throttle. The OOR error may occur for one of the sensors when the voltage is greater than 4.5 V or less than 0.5 V.
Typically, the OOC error occurs before the OOR error. When the higher of the two TPS is selected during the OOC error, the closed-loop control system may try to close the throttle and the engine may stall.
Also, when a TPS OOC fault is set due to the TPS sensors shorted together, engine shutdown may occur because indicated throttle was set higher than the throttle return fault diagnostic expected. When the throttle OOC fault occurs because one of the sensors is shifted high (which is most likely case), the system will use the high throttle position for the remainder of the ignition cycle. The engine stalls in most cases since the control system will drive the throttle into the stop.